Internal combustion engines supplied with petrol are conventionally provided with a butterfly valve which regulates the flow of air supplied to the cylinders. Typically, the butterfly valve has a valve body housing a valve seat engaged by a butterfly body which is keyed on a shaft in order to rotate between an open position and a closed position under the action of an electric actuator coupled to this shaft by means of a geared transmission. The shaft bearing the butterfly valve is associated with a position sensor, typically an angular encoder, adapted to detect the angular position of the shaft and therefore of the butterfly valve, in order to enable a control unit to control, in feedback, the electric actuator which determines the position of the butterfly valve; the position sensor in particular comprises a rotor which is coupled to the shaft and to a stator and which, in use, faces the stator and is adapted to detect the angular position of this stator.
At present the rotor of the position sensor is secured to the shaft of the butterfly valve after the production of this shaft typically by gluing; however, this working method is relatively complex and costly.